When a wall of the type having upper and lower plates and vertical studs is to be erected, the upper and lower plates of the wall are first tacked together. Then a workman using a conventional tape measure extending along the plates marks lines on both upper and lower plates. These lines represent the center lines of studs which are to be connected to the plates. The workman makes a series of these lines at locations 16 inches apart, the standard spacing between the center lines of adjacent studs. While this technique has been used for a number of years and is satisfactory, its use is time-consuming and somewhat tedious in view of the relatively long lengths of the plates. For these and other reasons, a need has arisen for improvements in locating the points along the upper and lower plates at which the studs are to be secured.